The desirability of injecting eggs has been recognized for some time. Initially, the purpose of injecting eggs was to prepare various vaccines using the egg as a growth medium for the vaccine. The vaccine was then harvested from the egg and used as desired.
More recent developments have aimed at injecting live eggs for the purpose of accomplishing some beneficial or therapeutic affect on the bird that will eventually hatch from the egg. One main advantage of injecting the egg rather than the live bird is basically related to the ease of injection. Eggs can be kept immobile and handled rather efficiently in comparison to newborn or older birds. Furthermore, in addition to the mechanical ease of injecting eggs, there also appear to be certain therapeutic advantages in either inoculating or otherwise treating embryos rather than live birds. These advantages have become particularly important in the poultry industry i.e., for chickens and turkeys.
Given the desirability of injecting eggs for both of the described purposes, several basic techniques have been attempted. These generally include either forcing fluids through the shell of an egg using some sort of pressurization system or physically forming an opening in the shell of an egg and then adding the desired fluid. In turn, injection using some type of needle arrangement has been one of the basic techniques for physically opening an egg for such purposes.
One goal of the devices that physically inject fluids is to deliver the fluid to a consistent position--i.e. vertically and horizontally--within each egg. For example, merely opening the top of an egg and delivering fluid into the air sack above the amniotic fluid is not appropriate for delivery of all substances. Some substances, in order to be effective, must be delivered directly into the amniotic fluid. Such delivery, however, raises an additional risk that when the injection device, commonly a needle, enters the amniotic fluid it risks injuring or even destroying the live embryo therein.
Therefore, a device which has the goal of injecting a large number of eggs on a relatively rapid basis, and of doing so while delivering a fluid substance to the same location within each egg, particularly when desired into the amniotic fluid, must deal with the reality that eggs, although generally of similar size, are not identical in size, even if taken from identical types of birds. The differences in size are particularly magnified compared to the normal operation of any well constructed machine in which the movement of the various parts is rather precisely and accurately governed by the physical parameters of the machine.
To date, there have been a number of attempts to orient eggs and injection devices with respect to one another so that each individual egg can be injected accurately, and a plurality of eggs can be handled with precision.
One example is U.S. Pat. No. 3,377,989 to Sandhedge in which injection needles are disposed within "egg size variation members" that are held in place by a cross bar. When the egg size variation member strikes an egg, it is permitted a slight variation of vertical travel to accommodate eggs of slightly different sizes.
Other methods are set forth in several patents assigned to the assignee of the present invention. These include U.S. Pat. Nos. 4,681,063 and 4,903,635 both to Hebrank, and U.S. Pat. No. 5,056,464 (Ser. No. 07/466,878, Filed Jan. 18, 1990) to Lewis. Each of these devices uses a novel combination of lifting eggs from their top portions, preferably by suction, in order to orient them with respect to injection needles. The Hebrank patents disclose a method of delivering fluid to the injection needles from a common supply, while the Lewis patent discloses an alternative advantageous arrangement for using a plurality of syringes associated with a respective plurality of injection needles.
In spite of the success obtained from the Hebrank and Lewis devices, however, there remains an addition problem in injecting eggs, particularly when they are delivered for injection in large groups. This problem is that when the eggs are delivered, typically in an egg tray or "flat", they may be positioned slightly off of a direct vertical orientation; i.e they are tilted. Accordingly, if the eggs are slightly tilted the ability to accurately and precisely control the travel of a needle will be somewhat lessened, even where the vertical relative travel between the egg and the needle is carefully controlled to account for differences in egg height. In other words, to date it has been difficult to accurately and precisely inject an egg with a device that includes a plurality of injection needles if an individual egg is tilted slightly off a direct vertical alignment.